Channel type induction furnace



United States Patent O 3,529,069 CHANNEL TYPE INDUCTION FURNACE Bengt Fredriksson and Kare Folgero, Vasteras, Sweden, assignors to Allmnna Svenska Elektriska Aktiebolaget, Vasteras, Sweden, a corporation of Sweden Filed Oct. 3, 1968, Ser. No. 764,671 Claims priority, application Sweden, Oct. 13, 1967, 14,057/67 Int. Cl. Hb 5/00 U.S. Cl. 13-31 10 Claims ABSTRACT OF THE DISCLOSURE Channel-type induction furnace tiltable about a shaft and provided with a lid for sealing against the atmosphere and having a furnace hearth in the form of an upright cylinder, the furnace having a charging means and an air-tight closing sluice applied near the lid.

BACKGROUND OF THE INVENTION The present invention relates to a channel-type induction furnace tiltable about a shaft and provided with a lid for vacuum and/ or pressure tight sealing.

Channel-type induction furnaces are known, even for vacuum purposes, in which the furnace hearth has the shape of a horizontal cylinder. The quantity of melt must in this case be limited so that there is a certain space above the melt in the furnace chamber. The melt sur-1 -face is often stationary under vacuum, the melt boils and in the case mentioned slag-coating and metal remnants will occur on the wall of the hearth about the surface of the melt in the axially situated parts. These deposits must be removed from time to time, which is often a problem.

Channeltype induction furnaces also exist for vacuum purposes which are equipped with a hearth in the form of an upright cylinder where a reiilling point is arranged in the side wall of the furnace and on the opposite side of the furnace hearth is a tapping point (teeming point). The furnace is tiltable and its upper part is sealed by a vacuumtight sealing lid, from which the evacuation conduits lead to the pump means.

-One disadvantage with the furnaces is the weakening vwhich occurs in the furnace wall at the refilling point, partly due to the slag deposits mentioned above which are here less than with horizontal cylinders, however, erosion in the walls, etc. It is also diflicult-to maintain effective vacuum due to perviousness in the walls, sealing problems at the filling opening, etc., where it is extremely difficult to make the ceramic material in the furnace wall tight. It must also be possible easily to remove the slag from the -melt surface and the slag deposits from the furnace wall and it is undesirable to tap off slag or slag deposits through the teeming opening (or through the filling opening).

SUMMARY OF THE INVENTION The invention provides a solution of these and other similar problems and relates to a channel-type induction furnace having a furnace hearth in the form of an upright cylinder, intended for vacuum and/ or pressure purposes. It is characterized in that itis equipped with charging means with an air-tight closing sluice applied at or near the lid. Such a furnace may have entirely vacuum and pressure tight side walls and bottom part, for example with a metallic, tight casing around the ceramic parts sealing against the inductors. After remo/val of the lid or upper part of the furnace with the charging means, slag can be removed and repairs carried out in the furnace wall, for example spraying the walls where holes have appeared or complete relining can be carried out. After a certain backwards tilting of the furnace slag can be scraped from the melt and also from the furnace walls and the opening at the lid, which has been diflcult with conventional furnaces of the vacuum type. Thus the slag need not be emptied through the teeming or lilling openings, which can thus be kept relatively free from slag.

With this type of furnace the advantage is also obtained that, after a certain tilting of the furnace, (when the 'vacuum or pressure has ceased) an inductor unit can be replaced without tapping oif the melt due to the tilting possibilities which are not obstructed by openings in the side walls, etc.

Pressure and/or vacuum treatment can take place in this furnace without the melt coming into contact with air at any stage in the treatment. For pressure treatment an inert gas, such as argon, is used.

In a preferred embodiment of the invention the furnace is made as a divided unit (vacuum or pressure tight connection between the parts) and the upper part is provided with a lid for vacuum and/ or pressure tight sealing, having a smaller diameter than the dividing plate. The lid can be placed so that, fromI a tapping and slag-removal point of view, tapping can be easily carried out after the furnace has been tilted backwards in relation to a stationary lid. The pressure against the lid during pressure treatment will due to the smaller pressure-absorbing surface be limited, and there are thus fewer problems regarding sealing and strength. The lid can be remo'ved quickly and the furnace charged rapidly and effectively without the loss of vacuum or pressure through the airtight sluice on the lid. By making the contact plane of the lid somewhat sloping the furnace can be tilted in relation to the stationary lid without previously lifting the lid. The lid may suitably be placed at the side of the furnace body so that after a certain limited backwards tilting of the furnace it can be charged with new melt at the side of the lid.

These and other advantages of the furnace construction described above will be seen fromthe following:

DESCRIPTION OF THE DRAWINGS FIG. 1 shows a channel-type inductor furnacey with inductors in upright and somewhat tilted position. FIG. 2 shows the same furnace in vertical section.

DESCRIPTION OF THE PREFERRED EMBODIMENT A channel-type induction furnace is shown with an upper part 11 and a lower part 12, vacuum pressure tightly joined by means of flange and sealing means. To the upper part is attached a smaller vacuum and pressure tight lid 13 with charging means for solid alloy constituents to be fed into the furnace through an air-tight sluice 14. On the lid 13 are also arranged measuring and inspection means 16, 15 of conventional type. As can be seen, the furnace side is smooth except for a teeming means (tapping means) for tapping off the furnace through a channel 17 leading from the bottom part of the hearth and a tapping spout 18. The spout part is connected to the furnace body by means of lflanges 19 and by means of surfaces of joining compound which does not prevent sintering, for example a heat-resistant cornpound in both contact surfaces of at least percent by weight magnesium oxide and chromium oxide, of which at least percent by weight is rbound as magnesium chromite MgO.Cr2O3. The flange and connection members may also be liquid-cooled in order to prevent them sintering in combination with the joint compound. Instead of the spout part 18 a vacuum or pressure head 20 may be applied at the flange member 19 and particularly in the last-mentioned case it is important to use screw and bolt members or other machine elements tokeep the head in position (see the inset gure near FIG. 2).

Below the furnace are applied in the normal manner one or more exchangeable inductors 21, preferably of vacuum type having coil, iron core and melt channel, and as known, from this channel the melt is stirred by magnetic pressure (pinchelfect). From the lid 13 evacuation conduits lead to the pump means and gas conduits for pressure treatment (not shown) from the container.

The furnace is tiltable about a tilting shaft 22 with the help of, for example, conventional hydraulic means 23. Tilting to the right (FIG. l) enables tapping through the spout 18 and tilting to the left in FIG. 1 enables tap ping olf the remainder of the melt and recharging with melt.

The furnace lid 13 is preferably applied along a somewhat sloping plane 24 and is vacuum and pressure tightly applied to the upper part 11 of the furnace body with its upright, cylindrical furnace hearth 25.

When the vacuum or pressure has ceased the furnace can be tilted backwards a certain angle (see the dotted position in FIG. l) without the lid 13 being noticeably lifted, after which melt can be tapped in at the side of the lid in the direction of the arrow A. Deslagging and removal of metal deposits may be carried out by scraping after removal of the lid 13 and a certain tilting of the furnace. Partial repairs of cracks and holes in the inner wall of the furnace may be carried out after removal of the lid and by spraying the wall with fresh compound or in some other way through the upper opening.

The furnace is tapped through the channel 17 and spout 18 after exchanging the head 20 and spout 18 and with the help of inert gas pressure at the surface of the melt. By removing the plug 27 or arranging for protective gas to be blown through this (lter principle) the melt can be prevented, by the introduction of protective gas at this part of the furnace near the spout, from reabsorbing damaging gases which have been previously removed during the degassing treatment. Owing to inert gas leaking in the pressure under the plug 27 will be somewhat higher than in the furnace space at 25, boiling is prevented here. As seen, the level below 27 is some- -what lower.

The iinal remnants of the melt can, after removal of the lid 13, be tipped over a slag runner (not shown) applicable at the lid opening, which s connected to the other ceramic parts of the furnace body. The furnace body and slag runner are coated on opposite parts with a non-sintering joint compound to prevent them being sintered together. When the lid 13 is removed or the head, the sealing surfaces can be protected by means of sealing rings 26 (see FIG. 1).

The slag runner according to the above can with advantage be made to function as a tapping spout for those parts of the melt (below a certain level) which are not tapped olf in degassed form through the furnace spout 18. The advantage of the head 20 is that no leakage through the not entirely tight parts of the compound and ceramic material in the furnace is obtained.

As seen in FIG. 2, the lid 13 is applied at a certain distance from the upper ceramic surfaces of the furnace body so that these opposite surfaces need not be made of special non-sintering material. However, in certain cases this may also be suitable. The sealings at the lid 13 and to the inductors 21 may -be liquid-cooled, as the sealings 19. The inductors should be of vacuum-tight type, for example according to U.S. Pat. No. 3,334,171.

The channel-type induction furnace according to the invention is used, for example, in the following way:

Melt, for example low-alloyed steel, is powered into the opening of the furnace (arrow A), after which the lid 13 is closed by tilting the furnace to upright position and the head 20 is applied at the spout part via the sealing .19. A vacuum is eected at the melt surface by means of evacuation and due to the inuence of the inductors the melt is kept hotand stirred so that all parts reach the surface of the melt or near the surface in turn and are thus freed from damaging contents and gases. During the treatment the constituents of the alloy are supplied in solid form through the air-tight sluices 14. When the vacuum treatment is complete inert gas is introduced through the plug 27 in order to maintain the degassing degree for the melt parts in the channel 17 as well, and the head 20 is replaced by the spout part 18. Pressure is then effected at the surface of the melt by the inert gas and teeming takes place at the spout 18, suitably in inert gas atmosphere. Thus tilting is unnecessary and teeming may take place without moving the spout. When most of the melt has been emptied in this way, the pressure ceases and the furnace is tilted to the left in the figure when the slag runner has been positioned. The slag is scraped off the melt and walls and the rest of the melt, together with other deposits, it tapped off through the slag runner. Recharging then takes place in the direction of the arrow A when the furnace has been tilted to a suitable position.

The invention according to the above can be varied in many ways within the scope of the following claims.

We claim:

1. An induction furnace for processing molten metal in vacuum or under pressure comprising:

a hearth of generally cylindrical configuration closed at both ends for gas tight sealing;

means mounting the hearth for rotation between a position in which the cylindrical configuration is vertical for processing of the metal and a position in which it is tilted from the vertical for charging and cleaning of the hearth;

a tapping opening in the side wall of the hearth for discharging metal by pressure Within the hearth when the cylindrical configuration is in the vertical position;

a charging opening in the upper wall of the hearth and a lid for closing the charging opening in a gas tight manner, the charging opening and lid having a considerably smaller cross section than that of the hearth whereby pressure on the lid is minimized.

2. A furnace as in claim 1 including:

charging means in said lid provided with a sluice closable in a gas tight manner.

3. A furnace as in claim 2 in which:

the charging opening and lid are displaced from the longitudinal axis of the hearth.

4. A furnace as in claim 3 in which:

the charging opening and lid are pressure tight against the atmosphere.

5. A furnace as in claim 3 in which:

the charging opening and lid are vacuum tight against the atmosphere.

6. A furnace as in claim 3 in which:

the hearth is divided into an upper part and a lower part in a plane transverse to its longitudinal axis, said charging opening and lid being in the upper part.

7. A furnace as in claim 3 in which:

the means mounting the hearth for rotation mounts the hearth for rotation about an axis close to its center of gravity.

8. A furnace as in claim 3 in which:

the charging opening and lid are on that side of the longitudinal axis of the hearth which is in the direction of the tilt from the vertical.

9. A furnace as in claim 3 including:

a slag runner for use with the charging opening when the lid is removed.

10. A furnace as in claim 3 including:

a protecting ring applicable to the charging opening for protecting the sealing surfaces of the opening when 5 6 the hearth is tilted and slag is being raked o the 3,187,394 6/ 1965 Tama et al. v.. 164-155 melt in the hearth through the opening. 3,191,247 6/ 1965 Holz 266-38 3,412,899 11/1968 Sutter 164-155 References Cited UNITED ATES P H. B. Pllmal'y Examiner 2,937,789 5/1960 Tama 13-31 X 5 Us, CL XR, 3,061,655 10/1962 Shaw 13-31 164 155 3,160,929 12/1964 Woodburn 164-155 

